A contemporary building is commonly heated by a central heating system. A central heating system is characterized by generation of heat in one room of the building and distribution of the generated heat to other rooms of the building. The heat is typically distributed by air forced through ductwork, by water running through pipes, or by steam flowing through pipes. The heat is generated by a heat generator. The heat generator can be a furnace, a burner, a heater, a boiler, or the like. Fuel for the heat generator can be natural gas, heating oil, kerosene, coal, peat, wood, biofuel, or the like. In some cases, the heat generator can use more than one type of fuel.
A thermostat is used to sense a temperature within the building and to use the sensed temperature as feedback to control the heat generator. For example, if the sensed temperature is greater than a setpoint temperature of the thermostat, then the thermostat changes an operating state of the heat generator from on to off. Conversely, if the sensed temperature is less than the setpoint temperature of the thermostat, then the thermostat changes the operating state of the heat generator from off to on. However, limiting control of the heat generator merely to changing the operating state often results in an underdamped control system in which gradients of thermal energy are produced within the building. For example, before the operating state of the heat generator changes from on to off, temperatures at some locations can be greater than the temperature sensed by the thermostat. Similarly, before the operating state of the heat generator changes from off to on, temperatures at some locations can be less than the temperature sensed by the thermostat. Such an underdamped control system can result in a level of comfort of people within the building that is less than what might otherwise be realized and can waste fuel.
Particularly in countries located in temperate climate zones, fuel consumed by central heating systems is a significant portion of all fuel consumed. For at least this reason, the European Commission issued Regulation No. 813/2013 on Aug. 2, 2013. This regulation states that certain heat generators, placed in the market and/or put into service after Sep. 26, 2015, must meet specific requirements with respect to efficiency. Manufacturers of heat generators have pursued various strategies to increase efficiency. Among these strategies have been efforts to better use the sensed temperature as feedback to control the heat generator. Rather than merely changing the operating state of the heat generator, the sensed temperature can be used to modulate operations of various components of the heat generator. For example, a position of a fuel valve of the heat generator and/or a speed of a blower of the heat generator can be incrementally controlled. In this manner, the overall control of the heat generator can approach that of a critically damped control system and thermal energy can be more uniformly distributed within the building. In comparison with a conventional control system, a control system that modulates operations of various components of the heat generator can improve the level of comfort of people within the building and can result in more efficient consumption of fuel.
An ability to communicate data between the thermostat and the heat generator can improve efforts to modulate operations of various components of the heat generator. To facilitate standardization of such communication, the OpenTherm® Association of Zoetermeer, Netherlands, has been established to manage the development and the licensing of versions of the OpenTherm® communication protocol and interface specification.